REGULARITIES OF HYDROGEN GENERATION BY HYDROLYSIS OF SODIUM BOROHYDRIDE ON IMMOBILIZED PLATINUM CATALYSTS

Abstract

Sodium borohydride hydrolysisis one of the most productive hydrogengeneration methods, which can be used, inparticular, to power fuel cells with a hydrogenanode. In alkaline solutions, the interaction of NaBH4 with water practically does not occur, which makes it possible to store such solutions for a longtime. However, in the presence of catalysts, the borohydride hydrolysis reaction actively proceeds at room temperature with the formation of hydrogenand sodium metaborate. More than 300 homogeneous and heterogeneous catalysts for the hydrolysis of sodium borohydride are known, among which the most active metal catalysts are nanodispersed rhodium, ruthenium, and platinum immobilized on various substrates. The activity of such catalysts depends on the conditions of the reduction and immobilization of metals, the nature of used precursors, the amount of active phase of the catalyst, and the type of substrate. In this work, platinum catalysts immobilized on several substrates are developed, and the regularities of hydrolysis of sodium borohydride in alkaline solution when using such catalysts in flowing flat and cylindrical reactors are investigated. Using various methods, platinum was deposited on carbon black and carbon cloth, onactivated granular carbon, on titanium crumb, and on synthetic cordierite of honey combstructure with surface, previously modified by alumina. It is shown that nanodisperse platinum catalysts immobilized on carbon black and carbon cloth and especially on synthetic cordierite of cellular structure with surface previously modified by Al2O3 layer are active and reliable. The average rate of hydrogen evolution during hydrolysis of NaBH4 on such catalysts increases with increasing flow rate of its solution through the reactor, but the degree of conversion of sodium borohydride decreases due to the reduced duration of contact of the solution with the catalyst. Nanodisperse platinum catalysts on surface-modified cordierite provide a highandstable rate of hydrogengeneration with moderate heating of NaBH4 solution (60±5°C). The use of hydrogen generators with such catalysts in combination with fuel cell batteries is promising for the creation of autonomous powers ources.